Electronic ignition timing control system for internal combustion engines

Abstract

In response to the input signal corresponding to the rotational speed of an internal combustion engine, a first read-only memory generates a binary coded signal indicative of the corresponding preliminarily written ignition retard angle from a predetermined angular position of the engine crankshaft, and in response to the input signal corresponding to the intake manifold vacuum a second read-only memory generates a binary coded signal indicative of the corresponding preliminarily written ignition retard angle. The output signals of the read-only memories are added together by an adder. A comparator compares the output signal of the adder with the number of clock pulses corresponding to the rotational angle of the crankshaft, and the ignition timing is determined by the output of the comparator.

What is claimed is: 
     
       1. An ignition timing control system for an internal combustion engine comprising: engine rotation detector means for generating an output pulse at each rotation of a predetermined angle of said engine;   clock means for generating clock pulses at a fixed frequency;   counter means, connected to said rotation detector means and said clock means, for counting the clock pulses of said clock means during a duration of the output pulse of said rotation detector means to generate an output signal related to the rotational speed of said engine;   engine load detector means for generating an output signal indicative of the load of said engine;   means for determining a desired ignition retard angle, connected to said counter means and said load detector means, for generating, in response to the output signals of said counter means and said load detector means, an output signal representing a desired ignition retard angle with respect to the rotational rotation and load of said engine;   frequency multiplier means, connected to said speed detector means, for frequency multiplying the output pulses of said rotation detector means by a constant value larger than one to generate output pulses;   reference position detector means, coupled to said engine, for generating an output signal at a predetermined reference position of said engine;   comparator means, connected to said means for determining a desired ignition retard angle, said frequency multiplier means and to said reference position detector means, for initiating a count of the output pulses of said frequency multiplier means in response to the output signal of said reference position detector means to generate an ignition timing signal when the count value thereof corresponds to contents of the output signal of said means for determining a desired ignition retard angle; and   igniter means, connected to said comparator means, for igniting said engine in synchronization with said ignition timing signal.   
     
     
       2. An ignition timing control system for an internal combustion engine comprising: engine rotation detector means for generating an output pulse at each rotation of a predetermined angle of said engine;   clock means for generating clock pulses at a fixed frequency;   counter means, connected to said rotation detector means and said clock means, for counting the clock pulses of said clock means during a duration of the output pulse of said rotation detector means to generate an output signal related to the rotational speed of said engine;   first memory means, connected to said counter means and having programmed therein data outputs corresponding to desired ignition retard angles with respect to the rotational speed of said engine, for generating one of said data outputs in said first memory means in response to the output signal of said counter means;   engine load detector means for generating an output signal indicative of the load of said engine;   second memory means, connected to said load detector means and having programmed therein data outputs corresponding to desired ignition retard angles with respect to the load of said engine, for generating one of said data outputs in said second memory means in response to the output signal of said load detector means;   parallel adder means, connected to said first and second memory means, for summing the data outputs of said first and second memory means to generate an output signal;   frequency multiplier means, connected to said rotation detector means, for frequency multiplying the output pulses of said rotation detector means by a constant value larger than one to generate output pulses;   reference position detector means, coupled to said engine, for generating an output signal at a predetermined reference position of said engine;   comparator means, connected to said parallel adder means, said frequency multiplier means and to said position detector means, for initiating a count of the output pulses of said frequency multiplier means in response to the output signal of said reference position detector means to generate an ignition timing signal when the count value thereof corresponds to contents of the output signal of said parallel adder means; and   igniter means, connected to said comparator means, for igniting said engine in synchronization with said ignition timing signal.   
     
     
       3. An ignition timing control system according to claim 2, wherein each of the data outputs of said first and second memory means in a binary signal representing an angle θ in degrees calculated in accordance with the following equation:   θ=α.M.N/360     wherein the symbol α is a desired retard angle in degrees, the symbol M is the number of the output pulses to be generated during one revolution of said engine, and the symbol N is the constant value of said multiplier means.   
     
     
       4. An ignition timing control system according to claim 3, wherein the output signal of said parallel adder means is a binary signal consisting of upper bits and lower bits, and wherein said comparator means includes: a first comparator, connected to said rotation detector means, said parallel adder means and said reference position detector means, for initiating to count the output pulses of said rotation detector means in response to the output signal of said reference position detector means to generate an output signal when the count value thereof reaches contents of the upper bits; and   a second comparator, connected to said first comparator said frequency multiplier means and said parallel adder means, for initiating to count the output pulses of said frequency multiplier means in response to the output signal of said first comparator to generate said ignition timing signal when the count value thereof reaches contents of the lower bits.